Data storage devices may be used in computers and other electronic equipment to store information in the form of data bits. Early data storage devices included computer punch-cards in which the data consisted of holes with millimeter dimensions. The punch-cards were fed into a computer and the data on the punch cards was read. Today, the punch-cards have been replaced by semiconductor chips and the millimeter-sized holes have been replaced with much smaller data bits.
As the data bits keep getting smaller and smaller, the bits may be positioned closer and closer together and the density of the data stored on a data storage device can be increased. When the data bits are of micrometer, sub-micrometer, or nanometer dimensions, the data storage device may be referred to as an ultra-high-density data storage device.
FIG. 1 illustrates a perspective view of an ultra-high-density data storage device 10. The ultra-high-density data storage device 10 includes a set of field emitters 100, an inorganic data storage layer 110 that is located below the field emitters 100, a micromover 120 that holds the inorganic data storage layer 110 below the field emitters 100 and that can position the inorganic data storage layer 110 at desired locations relative to the field emitters 100, and electrical connections 130 that can supply energy to the field emitters 100. When supplied with energy, the field emitters 100 can bombard the inorganic data storage layer 110 with electron beams and can transform nanometer-scaled portions of the inorganic data storage layer 110 from unwritten data bits, designated in FIG. 1 by the reference numeral 140, to written data bits, designated by the reference numeral 150. This transformation occurs via a writing process that will be discussed below.
As mentioned above, when writing data to the inorganic data storage layer 110, selected field emitters 100 are energized, through the electrical connections 130, and are made to bombard selected unwritten data bits 140 with electron beams. During the writing process, the electron beams are of sufficient power density to transform the bombarded unwritten data bits 140 from a first material state (e.g., a crystalline state, which may be assigned a “0” value) to a second material state (e.g., an amorphous state, which may be assigned a “1” value), upon appropriate cooling. Hence, a data bit having a value of “1” can be written to and stored on the inorganic data storage layer 110 by bombarding a crystalline, unwritten data bit 140 and by appropriately cooling the unwritten data bit 140 to form an amorphous, written data bit 150.
When erasing data from the inorganic data storage layer 110, selected field emitters 100 are energized, through the electrical connections 130, and are made to bombard selected written data bits 150 with electron beams. During the erasing process, the electron beams are of sufficient power density to transform the bombarded written data bits 150 from a second material state (e.g., an amorphous state, which may be assigned a “1” value) to a first material state (e.g., a crystalline state, which may be assigned a “0” value) through the application of a heating pulse with an appropriate temporal and spatial profile. For example, a data bit having a value of “0” can be restored on the inorganic data storage layer 110 by bombarding an amorphous, written data bit 150 and by appropriately heating and annealing the written data bit 150 to form a crystalline, erased data bit 140.
When reading data from the storage layer 110, the field emitters 100 again bombard the data bits 140, 150 with electron beams. However, instead of bombarding the data bits 140, 150 with electron beams that have sufficient energy to transform the data bits 140, 150 between the first and second material states discussed above, the field emitters 100 bombard the data bits 140, 150 with relatively low-power-density electron beams that do not effectuate a transformation but that do effectuate identification. Then, the interactions between the low-power-density electron beams and the data bits 140, 150 are monitored in order to read data.
Differences in the interactions monitored during the reading operation occur because the low-power-density beams interact differently with unwritten data bits 140 than with written data bits 150. For example, a low-power-density beam may generate fewer secondary electrons when bombarding a crystalline, unwritten data bit 140 than when bombarding an amorphous, written data bit 150. Therefore, by monitoring the interactions between the relatively low-power-density beam and the data bit 140, 150 that the beam is bombarding (e.g., by monitoring the number of secondary electrons generated), it becomes possible to determine whether the bombarded data bit 140, 150 is storing a “1” or a “0” value and to read data stored in the data storage layer 110.
Many of the storage materials typically used in the storage medium 110 illustrated in FIG. 1, such as inorganic phase-change materials, require a substantial amount of energy to transform an unwritten data bit 140 into a written data bit 150, and vice versa. In addition, traditional storage media are typically deposited in vacuum equipment by processes like evaporation or sputtering. Hence, in order to conserve energy during the writing or erasing processes and simplify the manufacturing process, it would be preferable to find alternate storage materials that require lower transformation energy and can be processed without vacuum equipment. The disadvantages of the prior art are overcome by embodiments described herein.